I made a couple of changes to the function to support recursively stepping into directories. I started messing around with this snippet in order to reproduce the functionality of using the Windows OpenFile dialog with a one-liner. Now it’s a bit more than a one-liner, but the GridView UI is actually pretty useful if you don’t know exactly what file you’re looking for.

function PickFile 
([string]$Path = $PWD)
{
    $results = Get-ChildItem $Path | Out-GridView -PassThru

    if ($results.Count -eq 1 -and $results.PSIsContainer)
    {
        PickFile $results.FullName
    }
    else
    {
        Write-Output -InputObject $results
    }
}